1. Field of the Invention
The present invention relates to an image display apparatus utilizing an electron beam irradiated to a phosphor screen, and can be applied to e.g., a field emission display (FED), a cathode ray tube (CRT) and the like.
2. Related Background Art
The large-sized structure of an image display apparatus such as a CRT is further required and vigorously researched. As the image display apparatus is large-sized, it is an important problem to make the image display apparatus thin and light weight and reduce cost of this image display apparatus.
However, in the CRT, an electron accelerated at high voltage is deflected by a deflecting electrode, and a phosphor on a face plate is excited. Therefore, when the CRT is large-sized, it is necessary to deepen the CRT in principle. Thus, it is difficult to provide the CRT which is thin and light weight. The inventors have made researches on a surface conduction electron-emitting device and an image display apparatus using this surface conduction electron-emitting device as an image display apparatus capable of solving the above problem.
For example, the inventors have applied, to a multi-electron beam source, an electric wiring method shown in FIG. 9 on trial. Namely, many surface conduction electron-emitting devices are two-dimensionally arranged, and are wired in a passive matrix shape as shown in FIG. 9 in the multi-electron beam source (field emission display (FED)).
In this FIG. 9, reference numerals 4001, 4002 and 4003 respectively designate surface conduction electron-emitting devices schematically shown, row-directional wirings and column-directional wirings. For convenience of drawing, 6xc3x976 matrices are shown in FIG. 9, but matrix scale is not limited to that. Devices sufficient to display a desired image may be arranged and wired.
FIG. 10 shows the structure of a cathode ray tube using this multi-electron beam source. This cathode ray tube is constructed of an external container bottom 4005 (there is also a case in which this external container bottom is described as a rear plate) having the multi-electron beam source, an external container frame 4007, a face plate 4006 having a phosphor layer 4008, and a metal back 4009. A high voltage is applied to the metal back 4009 by a high voltage power source 4010 through a high voltage introducing terminal 4011.
A suitable electric signal is applied to the row-directional wirings 4002 and the column-directional wirings 4003 to output a desired electron beam in the multi-electron beam source in which the surface conduction electron-emitting devices are wired in the passive matrix.
For example, a selection voltage Vs is applied to the one of the row-directional wirings 4002 in a selected row so as to operate the surface conduction electron-emitting devices in an arbitrary one row in the matrix. Simultaneously, a non-selection voltage Vns is applied to other row-directional wirings 4002 in non-selection rows.
In synchronization with this application, a driving voltage Ve for outputting the electron beam is applied to the column-directional wirings 4003. In accordance with this method, a voltage of Ve-Vs is applied to the surface conduction electron-emitting devices in the selected row, and a voltage of Ve-Vns is applied to the surface conduction electron-emitting devices in the non-selection row.
If Ve, Vs and Vns are set to voltages of suitable magnitudes, the electron beam of a predetermined desirable intensity is outputted from only the surface conduction electron-emitting devices in the selected row. Further, if the different driving voltage Ve is applied to each of the column-directional wirings, the electron beam of a different intensity is outputted from each of the devices in the selected row.
A responsive speed of the surface conduction electron-emitting device is a high speed. Therefore, if a time for applying the driving voltage Ve is changed, a time for outputting the electron beam is also changed.
The electron beam outputted from the multi-electron beam source by the above voltage application is irradiated to the metal back 4009 to which a high voltage Va is applied. Thus, the phosphor as a target is excited and emits light. Accordingly, for example, an image display apparatus is formed if a voltage signal corresponding to image information is suitably applied.
The phosphor used in the face plate of the above image display apparatus has xe2x80x9cluminance saturation characteristicsxe2x80x9d as described in xe2x80x9cPhosphor Handbook.xe2x80x9d (edited by Phosphor Study Companion Society and published by OHMSHA on Jun. 20, 1991) (pp. 265 to 266).
Namely, when current density of the electron beam irradiated to the phosphor is increased, light emitting efficiency of the phosphor is reduced, and luminance is saturated even if the current density is increased.
As mentioned above, since the phosphor has the xe2x80x9cluminance saturation characteristicsxe2x80x9d, the following problems are caused.
In case a current value of the electron beam is increased to obtain high luminance in the image display apparatus, the light emitting efficiency is reduced by the xe2x80x9cluminance saturation characteristicsxe2x80x9d and no luminance is improved as expected when the current density is increased.
It is confirmed that the phosphor is deteriorated in accordance with a supplied charge amount (coulomb amount) per unit area. In view of this point, it is also desirable to reduce the current density. In particular, the electron-emitting device of a transversal type such as the above surface conduction electron-emitting device, a field emission device (FE) or the like has a distribution of the high density current within one pixel irradiated by the electron beam as shown in FIG. 11. Accordingly, life shortening of the phosphor due to local deterioration of the phosphor in the highest density current portion becomes a serious problem. For example, the above one pixel in FIG. 3C is an area corresponding to the phosphor of each color shown by slanted lines between black matrices (shield members) 1010.
To solve the above problems of the prior art, an object of the present invention is to provide an image display apparatus in which the light emitting efficiency of a phosphor and luminance are improved.
Another object of the present invention is to provide an image display apparatus capable of improving luminance and obtaining a stable image for a long period by restraining local deterioration of the phosphor.
According to the present invention, there is provided an image display apparatus comprising an image forming member arranging a phosphor screen having a plurality of pixel areas therein, and a substrate arranged oppositely to the phosphor screen and arranging a plurality of electron-emitting devices therein, characterized in that each of the electron-emitting devices has a low potential side electrode and a high potential side electrode arranged side by side on the substrate, and an electron-emitting region located between both the electrodes, and each of the pixel areas has an inclination face inclined along a directed toward a center.